Acer Aspire ES14 not switch on

Measure the voltages to ground on all pins of transistors PQ19, PQ20, PQ21, PQ23 when the machine is turned on.

Transistors PQ19, PQ20, PQ21, PQ23 pin count:

PQ19
Pin 1 - Ground
Pin 2 - 2.5V
Pin 3 - Before press power key - 9.19V / After press power key - reduce nearly 0V

PQ20
Pin 1 - Ground
Pin 2 - Before press power key - 9.19V / After press power key - reduce nearly 0V
Pin 3 - 5V

PQ21
Pin 1 - Ground
Pin 2 - Before press power key - 9.14V / After press power key - reduce about 3V
Pin 3 - about 8V

PQ23
Pin 1 - Ground
Pin 2 - about 2.5V
Pin 3 - Before press power key - 9.18V / After press power key - reduce nearly 0V

Some of these measurements seems strange.

Please, post a clear pictures of transistors PQ19, PQ20, PQ21, PQ23 with a nearby surroundings.

Sorry, I've a mistake. I found PQ19 as PQ23 and PQ23 as PQ19.

cygron ha scritto:PQ21
Pin 1 - Ground
Pin 2 - Before press power key - 9.14V / After press power key - reduce about 3V
Pin 3 - about 8V

Pin 2 of transistor PQ21 is connected directly to pin 3 of transistor PQ19. How is it possible that you have different voltages on pin 2 of PQ21 and on pin 3 of PQ19?

Something should be wrong with your measurements, or you measured on wrong transistors.
Please, check your measurements on all pins of transistors PQ19, PQ20, PQ21, PQ23 again in the following cases:
a) Before pressing to the power button (machine turned off)
b) After pressing to the power button (machine turned on).

PQ19
Pin 1 - Ground
Pin 2 - about 2.0 V
Pin 3 - Before press power key - 9.1V / After press power key - reduce nearly 3V

PQ20
Pin 1 - Ground
Pin 2 - Before press power key - 9.1V / After press power key - reduce nearly 0V
Pin 3 - about 5V

PQ21
Pin 1 - Ground
Pin 2 - Before press power key - 9.1V / After press power key - reduce about 3V
Pin 3 - about 8V

PQ23
Pin 1 - Ground
Pin 2 - about 2.5V
Pin 3 - Before press power key - 9.10V / After press power key - reduce nearly 0V

Yes. Pin 2 of transistor PQ21 is connected directly to pin 3 of transistor PQ19 and measurement result is the same. Voltage on time is very short and it's difficult to measure voltage amout exactly. By the way, i tried to remove these transistors one by one for testing and when i remove PQ23, laptop condition is change. Power led is turn on. CPU fan is spin. But no display. PL13 - 5V, PL11 - 3V, PL8 - +1.0V_S5, PL7 - +1.8V_S5 and Charging Coil - 2.7V is on and stable. Others three coils have 0V.

Replace PQ19.

I try to Replacing PQ19 with some NPN transistor, but not success. Only remove with PQ23, laptop power led light on and cpu fan spin. With PQ23, laptop power led light does not turn on and no cpu fan spin.

cygron ha scritto:I try to Replacing PQ19 with some NPN transistor

Don't do that again, because you may damage the KBC chip this way.
Transistor PQ19 should have internal resistors.

Use the proper transistor for the replacement, or use a classic NPN transistor with added two 10kΩ resistors.

Remeasure the voltages to ground on all pins of transistors PQ19, PQ21 after replacing the transistor.

By the way, the voltage on pin 2 of PQ19, PQ23 should be different before and after pressing to the power button, but according to your posts these two voltages are the same in both cases. Check it.

Yes, the voltage on pin 2 of PQ19, PQ23 are different. Before pressing power keys both are 0V and after pressing power keys both are about 2.5V.

PQ19
Pin 1 - Ground
Pin 2 - Before press power key - 0V / After press power key - about 2.5 V
Pin 3 - Before press power key - 9.1V / After press power key - reduce nearly 3V

PQ20
Pin 1 - Ground
Pin 2 - Before press power key - 9.1V / After press power key - reduce nearly 0V
Pin 3 - Before press power key - 0V / After press power key - about 5V

PQ21
Pin 1 - Ground
Pin 2 - Before press power key - 9.1V / After press power key - reduce about 3V
Pin 3 - Before press power key - 0V / After press power key - about 8V

PQ23
Pin 1 - Ground
Pin 2 - Before press power key - 0V / After press power key - about 2.5V
Pin 3 - Before press power key - 9.10V / After press power key - reduce nearly 0V

Remove the transistors PQ17, PQ18, PQ21, PQ22, PQ42 from the board and remeasure the voltages to ground on all pins of transistors PQ19 and PQ20 before and after pressing to the power button.

PQ19
Pin 1 - Ground
Pin 2 - Before press power key - 0V / After press power key - about 1.2 V
Pin 3 - Before press power key - 9.1V / After press power key - reduce about 5V

PQ20
Pin 1 - Ground
Pin 2 - Before press power key - 9.1V / After press power key - reduce about 0V
Pin 3 - Before press power key - 0V / After press power key - about 9V


When press power key, power led lights on and off. CPU fan spin and stop.
Pressing power key about 4 or 5 times, laptop power led lights is on and CPU fan is spinning without stop. When laptop is running,
PQ19
Pin 1 - Ground
Pin 2 - 3V
Pin 3 - 0V

PQ20
Pin 1 - Ground
Pin 2 - 0V
Pin 3 - 13.1V

cygron ha scritto:PQ19
Pin 2 - Before press power key - 0V / After press power key - about 1.2 V

Previously there was about 2,5V. Which value is correct?
If this voltage appear only for a short time it is best to measure it with an oscilloscope to make sure.

Remove the transistors PQ20, PQ21 from the board and measure the voltage to ground on pad 3 on the place of transistor PQ20.

Yes. the voltage appear only for a short time and it's very difficult to measure exactly. But unfortunately i don't have any oscilloscope.

The voltage to ground on the place of transistor PQ20 - with or without press power key - 5.1V

cygron ha scritto:The voltage to ground on the place of transistor PQ20 - with or without press power key - 5.1V

Correct value should be around 12-14V.
Have you measured this voltage with removed transistor PQ21 as well?

If so, remeasure the voltages to ground on pad 3 on the place of transistors PQ20, PQ21 with removed transistors PQ20, PQ21, PQ42.

Remove transistors PQ20 and PQ21 and measure result is - pad 3 of transistor PQ20 (5.1V) and pad 3 of transistor PQ21 (12.1V)

Remove transistors PQ20, PQ21 and PQ42, measure result is - pad 3 of transistor PQ20 (13.1V) and pad 3 of transistor PQ21 (13.1V)

Check the transistor PQ42.
If it is good, solder all transistors except the PQ42 back to the board and measure the voltage to ground on pin 3 of transistors PQ20, PQ21 before and after pressing to the power button.

Found transistor PQ42 is fault. So i replace PQ42 with good one. But problem still exit. After replacing PQ42,

Voltage to ground on pin 3 of transistors PQ20 - without press power key (0V) / Press power key (12.1V)

Voltage to ground on pin 3 of transistors PQ21 - without press power key (0V) / Press power key ( about 8V )

Remove the transistors PQ12, PQ41 from the board and remeasure the voltage to ground on pin 3 of transistors PQ20 and PQ21 after pressing to the power button.

Measure voltage same as above.

Voltage to ground on pin 3 of transistors PQ20 - Press power key (12.1V)

Voltage to ground on pin 3 of transistors PQ21 - Press power key ( about 8-9V )